Production of artificial filaments, films, and other articles from organic polymerization products



2,347,545 PRODUCTION OF ARTIFICIAL FILAMENTS, FILMS, AND OTHER ARTICLESApril 1944- H. DREYFUS ET AL FROM ORGANIC POLYMERIZATION PRODUCTS FlledJuly 11, 1941 H DREYFUS R-WMONCRIEFF (.W-SAMMONS INVENTORS 7W -rroaulacs Patented Apr. 25, 1944 UNITED STATES PATENT OFFICE PRODUCTION OFARTIFICIAL FILAMENTS,

FILMS, AND OTHER ARTICLES FROM OR- GANIC POLYMERIZATION PRODUCTS HenryDreyfus, London, and Robert Wighton Moncrieff and Charles WilliamSammons, Spondon, near Derby, England, assignors to Celanese Corporationof America, a corporation of Delaware Application July 11, 1941, SerialNo. 401,992 In Great Britain May 31, 1940 1 Claim. (Cl.

formed in the presence of so-called stabilizin This invention relates tothe production of artificial filaments, films and other articles fromorganic polymerization products, and more parwith a reactive group ofanother molecule, water,

hydrochloric acid or a similar substance being eliminated during thereaction. A particularly useful class .of substances or polymers of thisnature, especially for the production of textile materials, may beformed, for example, by condensing diamines with dicarboxylic acids,with dihalides of dicarboxylic acids, or with diesters of dicarboxylicacids, or with disulphonic acids or their derivatives, or by condensingaminocarboxylic acids or aminosulphonic acids with themselves or witheach other. By a suitable choice of reagents it is possible to producesubstances with long chain molecules of high molecular weight which canbe converted into fibres or films. Preferably reagents are chosen whichhave no substantial tendency to condense with formation of cycliccompounds. This may be achieved by selecting the reagents in such a waythat the unit length of the resulting polymer consists of more than 6atoms in a chain, and preferably more than 7 atoms. In the case ofcondensing diamines with dicarboxylic acids, for example, the unitlength is arrived at by adding the number of atoms joining the twonitrogen atoms in the diamines plus 2, to the number ofatoms Joining thecarboxylic groups in the dicarboxylic acids plus 2.

The synthetic polymers produced by such reactions as described above maybe converted into shaped articles, for example filaments, foils, ribbonsor moulded articles, in various ways. For example, the polymers may befused in the pure condition and extruded into filamentary products,being set by the action of a cooling medium which may be a liquid, gasor vapour. Such a process is described, for example in U. S. applicationS. No. 333,952, filed May 8, 1940, now'Patent No. 2,303,340. Thepolymers, however, melt in general at temperatures of the order of 200-300 C., and at temperatures above or in the neighbourhood of the meltingpoint are found to be somewhat unstable, even when they have beenagents, e. g. in the presence of a slight excess of one of the componentreagents. Thus, one of the results of maintaining a polymer at atemperature slightly above its normal melting point is to degrade it sothat its viscosity is substantially lowered. In consequence, shapedarticles formed therefrom do not possess the tenacity or hardnessusually desired in such products. With a view to overcoming thistendency to degradation at temperatures above the melting point of thepolymer, it has been proposed to incorporate plasticisers in thematerials, and a particularly satisfactory method of shapingpoly-sulphonamides and like polymers in the fused condition has beenfound to comprise incorporating aproportion of a low-melting or liquidsulphonamide in the materials, and fusing and shaping the resultingcomposition; this method is described in greater detail in U. S.application S. No. 382,774, filed March 11, 1941.

Synthetic polymers of the type described above may be dissolved inphenols or in aliphatic carboxylic acids to concentrations of the orderof 40-45% and it has been suggested that the resulting solutions may bespun into filaments by dry or wet methods. In the case of employingphe-' nol solutions 0! the polyamides, dimculties may arise as a resultof the tendency of phenols themselves to become discoloured in thepresence of other materials, particularly oxygenated materials, e. g.air. Of the aliphatic acids, formic appears to be by far the best, sincepolyamides are more easily dissolved therein than in the other aliphaticacids, and since formic acid itself is more readily removed from shapedarticles than are the others. With formic acid, however though thepolyamide dissolves quite rapidly in the acid, it has hitherto beensupposed that it only dissolved to an extent of about 50 parts ofpolyamide for each 50 parts of acid; a solution of this composition isonly semi-solid at temperatures of the order of 25-30 C. The result ofthis has been that, in forming shaped articles, it has been necessary toremove a high proportion of formic acid shortly after the products havebeen shaped, which is undesirable, particularly in the case of formingartificial filaments, since it involves rather drastic treatment of thematerials while in their most delicatecondition.

We have now made the surprising discovery that the continued removal offormic acid from polyamide/formic acid solutions beyond theconcentration corresponding to apparent saturation results in theseparation of a solid material which has'been found to consist, not ofpure polyamide, but of a complex of formic acid and the polyamide. atordinary temperatures, melts at a temperature substantially below themelting point of the pure polyamide. Thus, in the case of the polymerformed by condensing hexamethylene diamine and adipic acid, there isseparated a solid which consists of approximately 72% of the polyamideand 28% of formic acid and which is found to melt at a temperature ofthe order of 40 0. below the melting point of the pure polyamide and cantherefore be extruded or otherwise shaped or moulded in the moltencondition at temperatures substantially below that point.

In producing a composition to be shaped, a polyamide may be agitatedwith an amount of formic acid sufficient to dissolve it to form, forexample, a 30-40% solution of polyamide, which will in general be foundto be a viscous liquid at ordinary temperatures. On raising thetemperature of this solution to about 70-100" C., formic acid may bevaporised and condensed outside the heating chamber so that the solutionbecomes more concentrated. Evaporation may be accelerated by workingunder reduced pres-' sure, if desired. Advantageously, the temperatureof evaporation is maintained at not substantially above 75 C., so thatsubstantially all tendency for the polyamide to become degraded iseliminated. When the concentration reaches a certain point, whichdepends upon the temperature of evaporation, solid composition commencesto separate from the liquid, and heating may be continued untilsubstantially the whole mass becomes solid within the temperature rangespecithe high concentration compositions accordingto the invention,extrusion may take place under pressure of any appropriate inert liquid,vapour or gas. The extruded materials may be received in an inertatmosphere contained in an enclosed chamber supplied with a draw-offintermediate between the extrusion orifice and the outlet for theextruded materials, as described in U. S. application S. No. 382,007,filed April 17, 1941, now Patent No. 2,335,922. In such a way, theextruded materials may be sufficiently cooled before coming into contactwith air that there is no tendency to discolour due to contact withoxygen. On the other hand, the extruded materials may be received,preferably after a short passage through a hot gaseous medium, in aliquid setting medium, which may be water, an aqueous solution, forexample, of a caustic alkali orof sodium formate, or an organic medium,e. g. a ketone such as, for example, acetone. The extruded materials arepreferably wound up at a rate somewhat in excess of that at which theyare extruded from the fusion chamber so that draw-down is applied tothem during their travel. After setting, the materials may be drawn downto a substantial extent, preferably in the presence of water, steam orother hydroxyl-containing compound, and the elasticity of the productsafter such a drawing treatment is surprisingly high.

The accompanying drawing shows, by way of This complex, which is a solidsolution.

example, apparatus which may be employed in spinning from a mass ofmolten composition in accordance with the present invention.

A narrow tube 3 surrounded by an electric heating element 4 is mountedin the upper end of a cylindrical casing 5 enclosing a chamber 6, andfeeds molten material to a spinning jet 1 which is closely surrounded byan electric heating element 8 to maintain the face of the jet and theclosely adjacent atmosphere at a desired elevated temperature. Filaments9, extruded from the jet 1, pass down the chamber 6 to a guide bar It]and thencethrough a small opening I I to a feed roller l2 and a suitablewinding, twisting and winding, or other take-up device, not shown. Theupper part of the chamber 6 is fed with an inert gas or vapor from alead l3, through holes M in an annular pipe I5. This inert gas or vaporis drawn off from the chamber through holes IS in an annular pipe ll, toa suction pipe l8. The annular pipe I! is situated at such a distancefrom the jet I that the filaments 9 before they reach the level of thepipe have cooled sufiiciently to be substantially undamaged by contactwith air. The suction applied through the holes IB also draws air intothe lower part of the chamber 6, through the circular hole I9 coveredwith fine wire gauze 20 in the base of the casing 5. A small amount ofair also enters through the opening H. A diaphragm 2 l mounted betweenthe annular pipe I! and the casing 5, prevents the passage of gases orvapors through this space, and electric heating elements 22 on theinside of the casing 5 can be employed for heating the atmosphere in thechamber 6.

Depending upon the method employed for setting the materials, there maystill remain in the filaments or other products after winding up and/ordrawing, a substantial proportion of formic acid. 'They may, therefore,be subjected to any appropriate washing treatment to remove this acid.For example, they may be immersed in a bath of a medium such as theliquid setting media described above, or sprayed or otherwise irrigatedtherewith.

Besides the formic acid, other agents may also be employed for thepurpose of facilitating the dissolution of the polyamide, for reducingthe melting point of the concentrated composition, and/or for increasingthe plasticity of the shaped and set materials. For example, othersolvents, e. g. trichloracetic acid, phenol, and resorcinol, may bepresent, or a low-melting sulphonamide may be incorporated in theoriginal solution prior to concentration, whereby a lower-meltingcomposition may be produced and products of greater plasticity formed.If it is not desired to retain the sulphonamide in the products, it maybe washed out in a manner similar to that employed for removing residualformic acid, due regard being paid to the solubility of the variouscomponents. Again, elfect materials may be incorporated in thecompositions at any suitable stage, e. g. by introduction duringproduction of the polyamide or into the relatively dilute solution. Suchmaterials may be, for example, delustring agents, e. g. titaniumdioxide, pigments or dyestuffs.

Reference has been made above more particularly to the polyamidesproduced by condensing diamines with diacids or their derivatives, or bycondensing aminoacids with themselves. While the invention is of thegreatest importance in connection with such polymers, other synthetic orlike methods,

.mass. The product is filmor fibre-forming polymers may be employed,

according to the 'invention, either alone or in association withpolyamides. For example, polymers formed by condensing dihalides withdiamines or with glycols may be employed.

Shaped materials according to the invention may have the form offilaments, yarns, films,

foils or other shaped articles formed by extrusion or may be in the formof plastic masses formed by moulding, e. g. by injection moulding, thefused compositions. filamentary products may be converted, if desired,into staple fibre, e. g. by cutting methods. The filamentary materialsand/or staple fibres may be converted into yarns suitable for use in theproduction of textile fabrics, and films, foils and the like may beemployed for wrapping purposes, for inter-layers in splinterless glassmanufacture, and for other purposes to which thermoplastic films and thelike have previously been applied.

The following example illustrates the invention:

Example A mixture of 100 parts by weight of hexamethylene diammoniu'madipate, 100 parts by weight of phenol, and 1.1 parts by weight ofadipic acid is heated at 190 C. for six hours under an atmosphere ofnitrogen to form a high viscosity polymer. The resulting mixture, aftercooling, is dissolved in cold 85% formic acid and the solution pouredinto a large excess of water to precipitate the polymer as a whitefibrous purified by thorou hly washing first with hot water and thenwith hot acetone.

20 parts by weight of the purified polymer are dissolved in so parts byweight ores/100 formic acid in the cold to yield a clear viscous liquidat 30 C. The solution so formed is heated in an atmosphere of nitrogenat 75 C. to evaporate formic acid. When the solution reaches aconpolymer, a solid having polymer/27.6% formic centration of about 54%the composition 72.4% acid begins to separate. Evaporation is continueduntil substantially all the mass is solid, and the solid material isthen separated from residual liquid.

A quantity of the precipitated solid solution is fused under nitrogen ina stainless steel vessel and passed through a heated narrow tube asdescribed in' U. S. application S. No. 375,762, filed January 24, 1941,to a jet having ten orifices each of diameter 0.2 mm. The conditions areadiusted so that the solution at the time when it reaches the jet has atemperature of substantially 255 C. and the jet face is maintained atthe same temperature by means of an electric heating coil closelysurrounding it. Under pressure of nitrogen the solution is extrudedaccording to U. S. application S. No. 382,007, now Patent No. 2,335,922,into a chamber, the upper part of which is filled with nitrogen. Aftersetting, the resulting filament bundle is freed from formic acid bywashing in dilute aqueous caustic alkali and in water, and during one ormore of the washing treatments the bundle is subjected to a stretchingoperation.

Having described our invention, what we desire to secure by LettersPatent is:

A composition for use in the production of artificial filaments, yarns,films and other shaped or molded articles by shaping or molding the samein a fused condition, which consists of approximately 72% of afilamentor film-forming polyamide formed by condensing hexamethylenediamine with adipic acid and 28% of formic acid, said composition beingsolid at ordinary temperature and melting at a temperature below themelting point of said polyamide.

HENRY DREYFUS. ROBERT WIGHTON MONCRIEFF. CHARLES WILLIAM SAMMONS.

